Multilayered container

ABSTRACT

Disclosed is a multilayered container having an intermediate layer comprising an oxygen-absorbable barrier resin composition showing excellent processability upon molding. Specifically disclosed is a multilayered container which comprises an inner layer and an outer layer each comprising an olefin resin and an intermediate layer provided between the inner layer and the outer layer and comprising an oxygen-absorbable barrier resin composition, wherein the oxygen-absorbable barrier resin composition has a cooling crystallization peak temperature lower than that of a base resin (an oxygen barrier resin) which constitutes the oxygen-absorbable barrier resin composition, the multilayered container is formed by a solid-phase forming process at a temperature lower by 1 to 15° C. than the cooling crystallization starting temperature (Tc2) of the base resin, and the body of the container shows a calorific value of less than 0.5 J/g by the isothermal crystallization after heating from 30° C. to 130° C. at a heating rate of 100° C./min in a thermal analysis of the body.

TECHNICAL FIELD

The present invention relates to a multilayered container having anintermediate layer consisting of an oxygen-absorbing barrier resincomposition which is excellent in molding processability.

BACKGROUND ART

An oxygen barrier resin such as an ethylene-vinyl alcohol copolymer(EVOH) is used as a resin which is layered on a layer of a thermoplasticresin such as a polyolefin to form a multilayered container (refer toPatent Document 1).

In molding a multilayered sheet which employs the oxygen barrier resinsuch as the ethylene-vinyl alcohol copolymer as an intermediate layer, asolid-phase forming is adopted from the viewpoint of improvement intransparency and mechanical properties. However, such solid-phaseforming has problems such as tearing and uneven thickness of the oxygenbarrier resin layer. Patent Document 1: Japanese Patent ApplicationPublication No. 2005-187808

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a multilayeredcontainer including an intermediate layer consisting of anoxygen-absorbing barrier resin composition which is excellent insolid-state molding processability.

The present invention provides a multilayered container comprising: aninner layer including an olefin resin; an outer layer including anolefin resin; and an intermediate layer provided between the inner layerand the outer layer and consisting of an oxygen-absorbing barrier resincomposition, wherein a cooling crystallization peak temperature of theoxygen-absorbing barrier resin composition is lower than that of a baseresin (an oxygen barrier resin) of the oxygen-absorbing barrier resincomposition, the multilayered container is solid-phase formed in atemperature range (T) which is lower by 1 to 15° C. than a coolingcrystallization starting temperature (Tc2) of the base resin, and, athermal analysis of a body portion of the container shows that an amountof heat released during isothermal crystallization after a temperatureraise from 30° C. to 130° C. at 100° C./min is less than 0.5 J/g.

The multilayered container of the present invention makes it possible toobtain a multilayered container including an intermediate layerconsisting of an oxygen-absorbing barrier resin composition which isexcellent in solid-state molding processability.

BEST MODES FOR CARRYING OUT THE INVENTION

A multilayered container of the present invention includes an innerlayer including an olefin resin, an outer layer including an olefinresin and an intermediate layer consisting of an oxygen-absorbingbarrier resin composition.

Examples of the olefin resins include: polyethylenes (PE) such as lowdensity polyethylene (LDPE), medium density polyethylene (MDPE), highdensity polyethylene (HDPE, linear low density polyethylene (LLDPE), andlinear very low density polyethylene (LVLDPE); polypropylene (PP); anethylene-propylene copolymer; polybutene-1; an ethylene-butene-1copolymer; a propylene-butene-1 copolymer; anethylene-propylene-butene-1 copolymer; an ethylene-vinyl acetatecopolymer; an ion-crosslinked olefin copolymer (ionomer); and a blendedmaterial thereof.

Examples of the gas barrier resin include an ethylene-vinyl alcoholcopolymer, a polyamide resin, and a polyester resin. These resins may beused alone or in combination of two or more.

In the present invention, the ethylene-vinyl alcohol copolymer isdesirably used as a resin which is particularly excellent in barrierproperties against oxygen and flavor components. As the ethylene-vinylalcohol copolymer, any publicly-known ethylene-vinyl alcohol copolymercan be used. For example, a saponified copolymer obtained by saponifyingan ethylene-vinyl acetate copolymer having an ethylene content of 20 to60 mol %, particularly 25 to 50 mol %, so that the saponification degreecan be 96 mol % or more, particularly 99 mol % or more can be used.

This ethylene-vinyl alcohol saponified copolymer needs to have amolecular weight enough to allow the saponified copolymer to be formedinto a film. Generally, the ethylene-vinyl alcohol saponified copolymerhas a viscosity of desirably 0.01 dL/g or more, particularly desirably0.05 dL/g or more, the viscosity being determined in a mixture solventwith a weight ratio of 85:15 of phenol to water, at 30° C.

Examples of the polyamide resin include: (a) an aliphatic, alicyclic orsemi-aromatic polyamide derived from a dicarboxylic acid component and adiamine component; (b) a polyamide derived from an aminocarboxylic acidor a lactam of an aminocarboxylic acid; a copolyamide thereof; and ablended material thereof.

Examples of the dicarboxylic acid component include: an aliphaticdicarboxylic acid having 4 to 15 carbon atoms, such as succinic acid,adipic acid, sebacic acid, decanedicarboxylic acid, undecanedicarboxylicacid, or dodecanedicarboxylic acid; and an aromatic dicarboxylic acidsuch as terephthalic acid or isophthalic acid.

Meanwhile, examples of the diamine component include: a linear- orbranched-chain alkylenediamine having 4 to 25 carbon atoms, particularly6 to 18 carbon atoms, such as 1,6-diaminohexane, 1,8-diaminooctane,1,10-diaminodecane, or 1,12-diaminododecane; an alicyclic diamine suchas a bis(aminomethyl)cyclohexane, bis(4-aminocyclohexyl)methane, or4,4′-diamino-3,3′-dimethyldicyclohexylmethane, or particularlybis(4-aminocyclohexyl)methane, 1,3-bis(aminocyclohexyl)methane, or1,3-bis(aminomethyl)cyclohexane; and an aromatic-aliphatic diamine suchas m-xylylenediamine and/or p-xylylenediamine.

Examples of the aminocarboxylic acid component include: an aliphaticaminocarboxylic acid such as, ω-aminocaproic acid, ω-aminooctanoic acid,ω-aminoundecanoic acid, or ω-aminododecanoic acid; and anaroma-aliphatic aminocarboxylic acid such as para-aminomethylbenzoicacid, or para-aminophenylacetic acid.

Of these polyamides, polyamides containing xylylene groups arepreferable, and specific examples thereof include: a homopolymer such aspoly-meta-xylylene adipamide, poly-meta-xylylene sebacamide,poly-meta-xylylene suberamide, poly-para-xylylene pimelamide, orpoly-meta-xylylene azelamide; a copolymer such as ameta-xylylene/para-xylylene adipamide copolymer, ameta-xylylene/para-xylylene pimelamide copolymer, ameta-xylylene/para-xylylene sebacamide copolymer or ameta-xylylene/para-xylylene azelamide copolymer; a copolymer obtained bycopolymerizing components of these homopolymers or these copolymers withan aliphatic diamine such as hexamethylenediamine; an alicyclic diaminesuch as piperazine; an aromatic diamine such aspara-bis(2-aminoethyl)benzene, an aromatic dicarboxylic acid such asterephthalic acid, a lactam such as ε-caprolactam, an ω-aminocarboxylicacid such as 7-aminoheptanoic acid, an aromatic aminocarboxylic acidsuch as para-aminomethyl benzoic acid; or the like. Particularly, apolyamide obtained from a diamine component mainly containingm-xylylenediamine and/or p-xylylenediamine and an aliphatic dicarboxylicacid and/or an aromatic dicarboxylic acid can be suitably used.

These polyamides containing xylylene groups are superior in gas barrierproperties to other polyamide resins, and thus preferable for achievingthe object of the present invention.

As for the polyamide in the present invention, a polyamide resin havinga terminal amino group concentration of 40 eq/106 g or more,particularly having a terminal amino group concentration exceeding 50eq/106 g is preferable from the viewpoint of suppressing the oxidativedegradation of the polyamide resin.

Oxidative degradation, i.e., oxygen absorption, of a polyamide resin,and the terminal amino group concentration of the polyamide resin haveclose relationship to each other. Specifically, when the terminal aminogroup concentration of a polyamide resin is within the above-describedrange which is relatively high, the oxygen absorption rate is reduced toa value of almost zero or close to zero. In contrast, if the terminalamino group concentration of a polyamide resin falls below theabove-described range, the oxygen absorption rate of the polyamide resintends to increase.

These polyamides also need to have molecular weights enough to allow thepolyamides to be formed into films, and the relative viscosity (ηrel)thereof determined at a concentration of 1.0 g/dl in sulfuric acid andat a temperature of 30° C. is desirably 1.1 or more, particularlydesirably 1.5 or more.

Examples of the polyester resin include a so-called gas barrierpolyester, which is a thermoplastic polyester derived from an aromaticdicarboxylic acid such as terephthalic acid and isophthalic acid and adiol such as ethylene glycol. The gas barrier polyester contains, in itspolymer chain, a terephthalic acid component (T) and an isophthalic acidcomponent (I) in a molar ratio of:

-   -   T:I=95:5 to 5:95,    -   particularly, 75:25 to 25:75, and an ethylene glycol        component (E) and a bis(2-hydroxyethoxy)benzene component (BHEB)        in a molar ratio of:    -   E:BHEB=99.999:0.001 to 2.0:98.0,    -   particularly, 99.95:0.05 to 40:60.        As the BHEB, 1,3-bis(2-hydroxyethoxy)benzene is preferable.

This polyester needs to have a molecular weight at least enough to allowthe polyester to be formed into a film, and generally the polyester hasan intrinsic viscosity [η] of desirably 0.3 to 2.8 dl/g, particularlydesirably 0.4 to 1.8 dl/g, the intrinsic viscosity being determined in amixture solvent with a weight ratio of 60:40 of phenol totetrachloroethane at a temperature of 30° C.

A polyester resin mainly made of polyglycol acid, or a polyester resinobtained by blending this polyester resin with a polyester resin derivedfrom the above-described aromatic dicarboxylic acid and theabove-described diol also can be used.

The oxygen-absorbing barrier resin composition preferably includes anoxidizable polymer. Here, the oxidizable polymer represents a polymerwhich exhibits an oxygen-absorbing function by being oxidized.

Examples of the oxidizable polymer include an oxidizable polymer havingunsaturated ethylenic bonds and the like, and the oxidizable polymer is,for example, derived by using a polyene as a monomer. Appropriateexamples of the polyene include conjugated dienes such as butadiene andisoprene. A homopolymer of a polyene; or a random or block copolymer ofa combination of two kinds or more of the above-described polyenes or ofa combination of the above-described polyene with a monomer other thanthe polyene, or the like can be used as the oxidizable polymer. Amongthe polymers derived from polyenes, polybutadiene, polyisoprene, naturalrubber, nitrile-butadiene rubber, styrene-butadiene rubber, chloroprenerubber, ethylene-propylene-diene rubber and the like are suitable,however, as a matter of course, the oxidizable polymer is not limitedthereto.

In addition, the oxidizable polymer having unsaturated ethylenic bondspreferably has a functional group. Examples of the functional groupinclude a carboxylic acid group, a carboxylic anhydride group, acarboxylic acid ester group, a carboxylic acid amide group, an epoxygroup, a hydroxy group, an amino group, a carbonyl group and the like.The carboxylic acid group and the carboxylic anhydride group areparticularly preferable from the viewpoint of compatibility and thelike. These functional groups may be located in a side chain of theresin or a terminal of the resin.

Examples of monomer used to introduce these functional groups includeethylenic unsaturated monomers each having the corresponding one of theabove-described functional groups.

As a monomer used to introduce a carboxylic acid group or a carboxylicanhydride group into an oxidizable polymer having unsaturated ethylenicbonds, an unsaturated carboxylic acid or a divertive thereof isdesirably used, and specific examples thereof include: anα,β-unsaturated carboxylic acid such as acrylic acid, methacrylic acid,maleic acid, fumaric acid, itaconic acid, citraconic acid, ortetrahydrophthalic acid; an unsaturated carboxylic acid such asbicyclo[2,2,1]hepto-2-ene-5,6-dicarboxylic acid; an α,β-unsaturatedcarboxylic acid anhydride such as maleic anhydride, itaconic anhydride,citraconic anhydride, or tetrahydrophthalic anhydride; and anunsaturated carboxylic acid anhydride such asbicyclo[2,2,1]hepto-2-ene-5,6-dicarboxylic acid anhydride.

The acid modification of the oxidizable polymer having unsaturatedethylenic bonds is carried out by using the oxidizable polymer havingunsaturated ethylenic bonds as the base polymer, and bygraft-copolymerization of an unsaturated carboxylic acid or a derivativethereof to the base polymer by use of a means known per se.Alternatively, the acid modification of the oxidizable polymer havingunsaturated ethylenic bonds can be produced by random-copolymerizationof the above-mentioned oxidizable polymer having unsaturated ethylenicbonds and an unsaturated carboxylic acid or a derivative thereof.

An oxidizable polymer having unsaturated ethylenic bonds and having acarboxylic acid group or a carboxylic anhydride group particularlysuitable from the viewpoint of dispersibility to the oxygen barrierresin is preferably a liquid resin containing a carboxylic acid or aderivative thereof in an amount to give an acid number of 5 KOH mg/g ormore.

When the content of the unsaturated carboxylic acid or the derivativethereof is within the above-described range, the oxidizable polymerhaving unsaturated ethylenic bonds is favorably dispersed in the oxygenbarrier resin, and the oxygen absorption is also performed smoothly.

When the oxidizable polymer having unsaturated ethylenic bonds isblended into the oxygen barrier resin, 1 g of the oxidizable polymerhaving unsaturated ethylenic bonds is preferably capable of absorbing2×10⁻³ mol or more, particularly 4×10⁻³ mol or more of oxygen in thepresence of a transition metal catalyst at a normal temperature. Inother words, when the oxygen-absorbing capability is the above-describedvalue or more, it is unnecessary to blend a large amount of theoxidizable polymer having unsaturated ethylenic bonds into the oxygenbarrier resin in order to cause favorable oxygen barrier properties tobe exhibited. Accordingly, this results in no reduction inprocessability and moldability of the resin composition into which theoxidizable polymer having unsaturated ethylenic bonds is blended.

The carbon-carbon double bond in the oxidizable polymer havingunsaturated ethylenic bonds used in the present invention is notparticularly limited. The carbon-carbon double bond may be located inthe main chain in a form of a vinylene group, or may be located in aside chain in a form of a vinyl group. In short, the carbon-carbondouble bond only needs to be oxidizable.

The oxidizable polymer having unsaturated ethylenic bonds is preferablycontained in the range of 1 to 30% by weight, particularly 3 to 20% byweight relative to the oxygen-absorbing barrier resin composition. Whenthe blended amount of the oxidizable polymer having unsaturatedethylenic bonds is within the above-described range, the resultingoxygen-absorbing layer has a sufficient oxygen-absorbing capability, andthe moldability of the resin composition can be maintained.

The oxygen-absorbing barrier resin composition preferably includes anoxidation catalyst.

Preferable examples of the oxidation catalyst include transition metalcatalysts containing a group VIII metal component of the periodic table,such as iron, cobalt and nickel. In addition, other examples includetransition metal catalysts containing: a group I metal component such ascopper and silver; a group IV metal component such as tin, titanium andzirconium; and a group V metal component such as vanadium, a group VImetal component such as chromium, and a group VII metal component suchas manganese. Of these metal components, the cobalt component has a highoxygen absorption rate, and thus particularly suitable for achieving theobject of the present invention.

The transition metal catalyst is used generally in a form of a lowvalent inorganic acid salt, a low valent organic acid salt or a lowvalent complex salt of the above-described transition metal.

Examples of the inorganic acid salt include: halides such as a chloride;sulfur oxyacid salts such as a sulfate; nitrogen oxyacid salts such as anitrate; phosphorus oxyacid salts such as a phosphate; a silicate; andthe like.

Meanwhile, examples of the organic acid salt include a carboxylate, asulfonate, and a phosphonate. A carboxylate is suitable for achievingthe object of the present invention, and specific examples thereofinclude transition metal salts of acetic acid, propionic acid, propionicacid, butanoic acid, isobutanoic acid, pentanoic acid, isopentanoicacid, hexanoic acid, heptanoic acid, isoheptanoic acid, octanoic acid,2-ethylhexanoic acid, nonanoic acid, 3,5,5-trimethylhexanoic acid,decanoic acid, neodecanoic acid, undecanoic acid, lauric acid, myristicacid, palmitic acid, margaric acid, stearic acid, arachic acid, lindericacid, tsuzuic acid, petroselinic acid, oleic acid, linoleic acid,linolenic acid, arachidonic acid, formic acid, oxalic acid, sulfamicacid, naphthenic acid and the like.

On the other hand, a complex with β-diketone or β-keto acid ester isused as the complex of the transition metal, and examples of theβ-diketone and the β-keto acid ester usable herein include acetylacetone, ethyl acetoacetate, 1,3-cyclohexadione,methylene-bis-1,3-cyclohexadione, 2-benzyl-1,3-cyclohexadione, acetyltetralone, palmitoyl tetralone, stearoyl tetralone, benzoyl tetralone,2-acetyl cyclohexanone, 2-benzoyl cyclohexanone,2-acetyl-1,3-cyclohexanedione, benzoyl-p-chlorobenzoylmethane,bis(4-methylbenzoyl)methane, bis(2-hydroxybenzoyl)methane,benzoylacetone, tri-benzoylmethane, diacetylbenzoylmethane,stearoylbenzoylmethane, palmitoylbenzoylmethane, lauroylbenzoylmethane,dibenzoylmethane, bis(4-chlorobenzoyl)methane,bis(methylene-3,4-dioxybenzoyl)methane, benzoylacetylphenylmethane,stearoyl(4-methoxybenzoyl)methane, butanoylacetone, distearoylmethane,acetylacetone, stearoylacetone, bis(cyclohexanoyl)methane,dipivaloylmethane and the like.

Those skilled in the art can easily set the content of theabove-mentioned oxidizable polymer having unsaturated ethylenic bonds tomake the above-described cooling crystallization peak temperature lowerthan that of the base resin. Generally, the content is 1 to 30% byweight, preferably 3 to 20% by weight, relative to the total weight ofthe oxygen-absorbing barrier resin composition.

Those skilled in the art can also easily set the content of theoxidation catalyst to make the above-described cooling crystallizationpeak temperature lower than that of the base resin. Generally, thecontent is 100 to 1000 ppm, preferably 200 to 500 ppm, in terms of theamount of metal, relative to the total weight of the oxygen-absorbingbarrier resin composition.

The oxygen-absorbing barrier resin composition may be a blended materialof the oxygen barrier resin and the oxidizable polymer. Alternatively,the oxygen-absorbing barrier resin composition may be blended with anadditive such as a nucleating agent or compatibilizer, as a thirdcomponent. Particularly, from the viewpoint of improvement inoxygen-absorbing properties, processability and transparency and otherviewpoints, the oxidizable polymer or the additive is preferably bondedto the oxygen barrier resin. Note that the above-described bond can bechecked by nuclear magnetic resonance, a Fourier transform infraredspectrometer or the like.

In the multilayered container of the present invention, the coolingcrystallization peak temperature of the oxygen-absorbing barrier resincomposition is lower than that of the base resin (oxygen barrier resin)of the oxygen-absorbing barrier resin composition.

Such a condition of the above-described cooling crystallization peaktemperature makes it possible to obtain an oxygen-absorbing barrierresin composition which is excellent in processability, withcrystallization thereof during solid-phase forming being prevented orbeing less frequent.

In addition, the multilayered container of the present invention issolid-phase formed in a temperature range lower by 1 to 15° C. than thecooling crystallization starting temperature (Tc2) of the base resin.With such a molding condition, an amount of heat released which will bedescribed later can be set in an appropriate range, and a multilayeredcontainer which has the oxygen-absorbing capability and is excellent inoxygen barrier properties can be obtained. The multilayered container ofthe present invention is preferably solid-phase formed in a temperaturerange (T) which is lower by 1 to 15° C. than Tc2, more preferablysolid-phase formed in a temperature range lower by 3 to 14° C. than Tc2.In addition, the multilayered container of the present invention is suchthat, a thermal analysis of the body portion of the container shows thatthe amount of heat released during isothermal crystallization after atemperature raise from 30° C. to 130° C. at 100° C./min is less than 0.5J/g. When the amount of heat released is in such a range, it is possibleto obtain a multilayered container which is excellent in containerappearance and mechanical properties, and which has excellent oxygenbarrier properties with oxygen-absorbing capability.

In addition, the multilayered container of the present invention is suchthat, x-ray diffraction measurement shows that an intensity ratio I/I₀of an intensity (I) of an (110) plane to a baseline (I₀) is 4 or more inat least the body portion of the container. When the intensity ratioI/I₀ is in such a range, it is possible to obtain a multilayeredcontainer which is further excellent in transparency and mechanicalproperties, and which has excellent oxygen barrier properties withoxygen-absorbing capability. The intensity ratio I/I₀ is more preferably4 to 10.

The multilayered container of the present invention may include anadhesive resin interposed between any adjacent resin layers, ifnecessary.

Examples of such an adhesive resin include a polymer including acarboxylic acid, a carboxylic anhydride or a carboxylic acid in the mainchain or side chains thereof at a concentration of 1 to 700milliequivalent (meq) per 100 g of resin, preferably 10 to 500 meq per100 g of resin.

Examples of the adhesive resin include an ethylene-acrylic acidcopolymer, an ion-crosslinked olefin copolymer, maleic anhydride graftedpolyethylene, maleic anhydride grafted polypropylene, acrylic acidgrafted polyolefin, an ethylene-vinyl acetate copolymer, copolymerizedpolyester, copolymerized polyamide and the like, and the adhesive resinmay be a combination of two or more of these resins.

These adhesive resins are useful for lamination by co-extrusion,sandwich lamination or the like. A thermosetting adhesive resin ofisocyanate type or epoxy type can also be used.

A layer structure in which the oxygen-absorbing barrier resincomposition of the present invention is used can be selectedappropriately, depending on the use mode and required function. Inparticular, a structure having at least one oxygen barrier layer ispreferable because the life time of the oxygen absorption layer can beimproved.

In a laminated body in which the oxygen-absorbing barrier resincomposition of the present invention is used, a deodorant or anadsorbent for oxidation by-products is preferably blended into theoxygen absorption layer or any one of the other layers, particularly alayer inside the oxygen absorption layer, in order to trap by-productsgenerated in oxygen absorption.

Examples of the deodorant and the adsorbent include ones known per se.Specifically, the examples include naturally occurring zeolite,synthetic zeolite, silica gel, active carbon, impregnated active carbon,activated clay, activated aluminum oxide, clay, diatomaceous earth,kaolin, talc, bentonite, sepiolite, attapulgite, magnesium oxide, ironoxide, aluminum hydroxide, magnesium hydroxide, iron hydroxide,magnesium silicate, aluminum silicate, synthetic hydrotalcite andamine-supporting porous silica. Of these, the amine-supporting poroussilica is preferable from the viewpoint of reactivity with aldehydes,which are oxidation by-products. A so called high silica zeolite, whichhas high silica/alumina ratio, is preferable from the viewpoints ofexhibiting excellent properties to absorb various oxidation by-productsand being transparent.

The silica/alumina ratio (molar ratio) of the high silica zeolite ispreferably 80 or more, more preferably 90 or more, further preferably100 to 700.

In certain highly humid conditions, a zeolite with a low silica/aluminaratio has properties in which absorbability of oxidation by-products isdeteriorated. In contrast, in such highly humid conditions, a zeolitewith the high silica/alumina ratio has properties in which absorbabilityof oxidation by-products improve. Accordingly, the zeolite with such ahigh silica/alumina ratio is particularly effective when used in apackage for packaging contents containing water. The exchanged cationsof the high silica zeolite need to be one kind of, or a combination oftwo or more kinds of: alkali metal ions such as sodium, lithium andpotassium ions; and alkaline earth metal ions such as calcium andmagnesium ions. In this case, one containing at least sodium cations asthe exchanged cations is preferable. A particularly preferable exampleis one in which substantially all exchanged cations are sodium ions.

The multilayered container of the present invention is made of a flangeportion, a body portion and a bottom portion. The ratio H/D of theheight H to the diameter D of the multilayered container is in the rangeof preferably 2.0 or less, more preferably 1.6 to 0.8, from theviewpoint of processability.

A packaging container which employs the multilayered structure of thepresent invention is useful as a container capable of preventing flavordeterioration of the contents due to oxygen.

Examples of contents which can be packaged include contents which easilydegrade in the presence of oxygen. Specifically, the examples include:beverages such as beer, wine, fruit juice, carbonated soft drink, oolongtea and green tea; foods such as fruit, nuts, vegetables, meat products,infant food, coffee, jam, mayonnaise, ketchup, edible oil, dressing,various kinds of sauce, foods boiled down in soy or the like, and dairyproducts; others such as medicines, cosmetics and gasoline; and thelike. However, contents which can be packaged are not limited thereto.

Examples

The present invention will be described in further details on the basisof Examples; however, the present invention is not limited thereto.

1. Determination Methods

(1) Solid-Phase Forming in Temperature Range (T) Lower by 1 to 15° C.than Cooling Crystallization Starting Temperature (Tc2) of Base Resin

A measurement sample was cut out of the body portion of a multilayeredcontainer. The sample was heated from 0° C. to 230° C. at a rate of 10°C./min, held for 5 minutes, and thereafter cooled to 0° C. at a rate of10° C./min, by using a DSC measurement differential scanning calorimeter(DSC6220: manufactured by Seiko Instruments Inc.), to determine thecooling crystallization starting temperature (Tc2) of a base resin. As aresult the temperature was found to be 162° C.

The temperature difference (Tc2)−(T) was found by subtracting a moldtemperature (T) from the cooling crystallization starting temperature(Tc2) of 162° C. to check whether or not solid-phase forming wasperformed in a temperature range (T) lower by 1 to 15° C. than thecooling crystallization starting temperature (Tc2) of 162° C. of thebase resin.

(2) Amount of Heat Released During Isothermal Crystallization

A measurement sample was cut out of the body portion of a multilayeredcontainer. The sample was heated from 30° C. to 130° C. at a rate of100° C./min and held for 30 minutes, by using a DSC measurementdifferential scanning calorimeter (DSC6220: manufactured by SeikoInstruments Inc.) to determine the amount of heat released duringisothermal crystallization.

(3) X-Ray Diffraction Intensity Ratio I/I₀

A measurement sample was taken out of the body portion of a multilayeredcontainer. A diffraction profile of the sample was determined by using amicro X-ray diffractometer (PSPC-150C: manufactured by Rigakucorporation). The determination was conducted as follows: x-rays wereformed into narrow beams using a collimator; the narrow beams werecaused to perpendicularly enter a surface of multiply-stacked sample;the height direction of the container was set to be perpendicular to theplane containing the X-ray optic axis and curved PSPC (intensity oforientation in the height direction); diffraction intensity in a rangeof Bragg angle 2θ=0 to 100° was accumulated by using the curved PSPC;the diffraction due to air was subtracted from the obtained x-raydiffraction profile; and then the intensity ratio I/I₀ was calculated,where the peak intensity at 2θ=14.5° (corresponding to the 110 plane ofpolypropylene) was designated as I, and the peak intensity at 2θ=15.5°was designated as I₀.

2. Evaluation

The appearance of a multilayered container was visually observed tocheck appearance of the container such as vertical stripe-shapedirregularity (irregularity due to the stretching during molding),surface unevenness, whitening, and evenness in the thickness (unevennessin container thickness), as well as mechanical properties such as impactresistance (drop strength). If such phenomena were not observed in themultilayered container, the multilayered container was marked with ∘,and if such phenomena were observed in the multilayered container, themultilayered container was marked with ×.

Example 1

Base resin (oxygen barrier resin) pellets made of an ethylene-vinylalcohol copolymer resin (copolymerized with 32 mol % of ethylene)(EP-F171B: KURARAY CO., LTD.) was mixed with a transition metal catalystof cobalt neodecanoate (cobalt content: 14 wt %) (DICANATE 5000:Dainippon Ink and Chemicals, Incorporated) by using a tumbler.Accordingly, 350 ppm of cobalt neodecanoate in terms of cobalt contentwas evenly attached onto the surface of the above-described base resinpellets.

Next, by using a twin screw extruder (TEM-35B: TOSHIBA MACHINE CO., LTD)equipped with a strand die at the outlet portion thereof was used toprepare oxygen-absorbing barrier resin composition pellets. The twinscrew extruder was operated at screw revolution speed of 100 rpm and wasevacuated through a low vacuum vent. Therein, 50 parts by weight ofmaleic anhydride-modified polybutadiene having an acid number of 40 mgKOH/g (M-2000-20: Nippon Petrochemicals Co., Ltd.) was added dropwise byusing a liquid feeder to 950 parts by weight of the base resin with thecobalt attached thereto, and then strands were formed at a moldtemperature of 200° C. Thus, oxygen-absorbing barrier resin compositionpellets were prepared.

Then, a multilayered sheet of five layers was formed by using threetypes of resins: a polypropylene resin (EC9J: Japan PolypropyleneCorporation); an adhesive resin (ADMERQF551, Mitsui Chemicals, Inc.);and the oxygen-absorbing barrier resin composition pellets prepared asabove.

The structure and thickness of the layers were as follows: polypropylenelayer (557 μm)/adhesive resin layer (24 μm)/oxygen-absorbing barrierresin composition layer (38 μm)/adhesive resin layer (24μm)/polypropylene layer (557 μm). The total thickness of themultilayered sheet is 1200 μm.

The multilayered sheet was cut into a 30 cm square. Then, the sheet washeated to 148° C. with a far-infrared heater, and solid-phase formedinto a multilayered container at a drawing ratio H/D=1.3 by using a plugassisted vacuum-pressure forming machine.

The obtained multilayered container was subjected to the determinationof the temperature difference (Tc2−T) obtained by subtracting the moldtemperature (T) from the cooling crystallization starting temperature(Tc2) of 162° C., of the amount of heat released during isothermalcrystallization, and of the x-ray diffraction intensity ratio I/I₀, andthe evaluation of the container was made.

Example 2

A multilayered container was solid-phase formed in the same manner asExample 1, except that the sheet heating temperature was set to 159° C.Then, the multilayered container was subjected to the determination andthe evaluation.

Example 3

A multilayered container was solid-phase formed in the same manner asExample 1, except that the drawing ratio H/D was set to 1.6. Then, themultilayered container was subjected to the determination and theevaluation.

Comparative Example 1

A multilayered container was solid-phase formed in the same manner asExample 1, except that the base resin was used as the intermediatelayer. Then, the multilayered container was subjected to thedetermination and the evaluation.

Comparative Example 2

A multilayered container was solid-phase formed in the same manner asExample 1, except that the base resin was used as the intermediate layerand the sheet heating temperature was set to 158° C. Then, themultilayered container was subjected to the determination and theevaluation.

Comparative Example 3

A multilayered container was tried to be solid-phase formed in the samemanner as Example 1, except that the base resin was used as theintermediate layer and the drawing ratio in molding was set to 1.6.However, with this condition, the solid-phase forming failed.Accordingly, neither determination of the amount of heat released duringisothermal crystallization and the x-ray diffraction intensity ratioI/I₀ nor the evaluation of the container was performed.

Comparative Example 4

A multilayered container was molded in the same manner as Example 1,except that the sheet heating temperature was set to 130° C. Then, themultilayered container was subjected to the determination and theevaluation.

Comparative Example 5

A multilayered container was molded in the same manner as Example 1,except that the base resin was used as the intermediate layer and thesheet heating temperature was set to 130° C. Then, the multilayeredcontainer was subjected to the determination and the evaluation.

Comparative Example 6

A multilayered container was molded in the same manner as

Example 1, except that the sheet heating temperature was set to 180° C.and the drawing ratio H/D was set to 0.8. Then, the multilayeredcontainer was subjected to the determination and the evaluation.

Table 1 shows check results of the temperature differences (Tc2−T) eachobtained by subtracting the mold temperature (T) from the coolingcrystallization starting temperature (Tc2) of 162° C. as well as thedetermination results of the amount of heat released during isothermalcrystallization and x-ray diffraction intensity ratio I/I₀. Table 2shows evaluation results of the multilayered containers.

As is clear from Table 2, the present invention makes it possible toobtain a multilayered container including an intermediate layerconsisting of an oxygen-absorbing barrier resin composition which isexcellent in solid-state molding processability. As a result, themultilayered container has excellent container appearance and excellentmechanical properties.

TABLE 1 Solid state molding Molding conditions Cooling Sheetcrystallization Amount of heat X-ray heating Drawing peak Temperaturereleased during diffraction Determined temperature ratio temperaturedifference isothermal intensity portion Layer structure (T) (° C.) (H/D)(Tc2) (° C.) (Tc2 − T) crystallization ratio (I/I₀) Example 1 BodyPP/adhesive/oxygen 148° C. 1.3 154° C. 14° C. 0.06 6.5 portion absorbingmaterial/adhesive/PP Example 2 Body PP/adhesive/oxygen 159° C. 1.3 154°C.  3° C. 0.46 8.6 portion absorbing material/adhesive/PP Example 3 BodyPP/adhesive/oxygen 148° C. 1.6 154° C. 14° C. 0.13 6.1 portion absorbingmaterial/adhesive/PP Comparative Body PP/adhesive/base 148° C. 1.3 160°C. 14° C. 0.09 7.9 Example 1 portion material resin/adhesive/PPComparative Body PP/adhesive/base 158° C. 1.3 160° C.  4° C. 0.16 9.7Example 2 portion material resin/ adhesive/PP ComparativePP/adhesive/base 148° C. 1.6 — 14° C. — — Example 3 material resin/adhesive/PP Comparative Body PP/adhesive/oxygen 130° C. 1.3 154° C. 32°C. 0.00 7.6 Example 4 portion absorbing material/adhesive/PP ComparativeBody PP/adhesive/base 130° C. 1.3 160° C. 32° C. 0.07 9.4 Example 5portion material resin/ adhesive/PP Comparative Body PP/adhesive/oxygen180° C. 0.8 154° C. −18° C.   0.52 3.1 Example 6 portion absorbingmaterial/adhesive/PP

TABLE 2 Solid-state molding Evaluation Mechanical Container appearancecharacteristics Vertical Unevenness in evenness in impact stripe-shapedcontainer the resistance (drop irregularity surface Whitening thicknessstrength) Example 1 ∘ ∘ ∘ ∘ ∘ Example 2 ∘ ∘ ∘ ∘ ∘ Example 3 ∘ ∘ ∘ ∘ ∘Comparative x x ∘ ∘ ∘ Example 1 Comparative x x ∘ ∘ ∘ Example 2Comparative — — — — — Example 3 Comparative ∘ ∘ x x ∘ Example 4Comparative ∘ ∘ x x ∘ Example 5 Comparative ∘ ∘ ∘ ∘ x Example 6

1. A multilayered container comprising: an inner layer including anolefin resin; an outer layer including an olefin resin; and anintermediate layer provided between the inner layer and the outer layerand consisting of an oxygen-absorbing barrier resin composition, whereina cooling crystallization peak temperature of the oxygen-absorbingbarrier resin composition is lower than that of a base resin (an oxygenbarrier resin) of the oxygen-absorbing barrier resin composition, themultilayered container is solid-phase formed in a temperature range (T)which is lower by 1 to 15° C. than a cooling crystallization startingtemperature (Tc2) of the base resin, and, a thermal analysis of a bodyportion of the container shows that an amount of heat released duringisothermal crystallization after a temperature raise from 30° C. to 130°C. at 100° C./min is less than 0.5 J/g.
 2. The multilayered containeraccording to claim 1, wherein x-ray diffraction measurement shows thatan intensity ratio I/I₀ of an intensity (I) of an (110) plane to abaseline (I₀) is 4 or more in at least the body portion of thecontainer.
 3. The multilayered container according to claim 1, whereinthe oxygen-absorbing barrier resin composition includes a resin obtainedby blending, with the base resin, an oxidizable polymer havingunsaturated ethylenic bonds and an oxidation catalyst.
 4. Themultilayered container according to claim 1, wherein the base resin isan ethylene-vinyl alcohol copolymer resin.